San Francisco's cable cars were invented in 1869 by London-born engineer Andrew Hallidie, who got the idea by way of serendipity. As the story goes, Hallidie was watching a team of overworked horses haul a heavily laden carriage up a steep San Francisco slope. As he watched, one horse slipped and the car rolled back, dragging the other tired beasts with it. At that moment Hallidie resolved that he would invent a mechanical contraption to replace such horses, and just 4 years later, in 1873, the first cable car made its maiden run from the top of Clay Street. Promptly ridiculed as "Hallidie's Folly," the cars were slow to gain acceptance. One early onlooker voiced the general opinion by exclaiming, "I don't believe it--the damned thing works!"

Even today, many visitors have difficulty believing that these vehicles, which have no engines, actually work. The cars, each weighing about 6 tons, are hauled along by a steel cable, enclosed under the street in a center rail. You can't see the cable unless you peer straight down into the crack, but you'll hear its characteristic clickity-clanking sound whenever you're nearby. The cars move when the gripper (not the driver) pulls back a lever that closes a pincerlike "grip" on the cable. The speed of the car, therefore, is determined by the speed of the cable, which is a constant 9 1/2 miles per hour--never more, never less.

The two types of cable cars in use hold, respectively, a maximum of 90 and 100 passengers, and the limits are rigidly enforced. The best views are had from the outer running boards, where you have to hold on tightly when taking curves. Everyone, it seems, prefers to ride on the running boards.

Often imitated but never duplicated, similar versions of Hallidie's cable cars have been used throughout the world, but all have been replaced by more efficient means of transportation. San Francisco planned to do so, too, but the proposal was met with so much opposition that the cable cars' perpetuation was actually written into the city charter in 1955. This mandate cannot be revoked without the approval of a majority of the city's voters--a distant and doubtful prospect.

San Francisco's three existing lines form the world's only surviving system of cable cars, which you can experience for yourself should you choose to wait in the endless boarding line (up to a 2-hour wait in summer).